1. Field of the Invention
The present invention relates to ink jet printers, and particularly to a small ink jet printer that has a narrow lateral width for the runway portion and the overrun portion of the ink carriage.
2. Description of the Background Art
Referring to FIG. 1, a conventional ink jet printer 261 includes a scan guide 264 formed of a linear metal rod, and an ink carriage 263 that moves linearly along scan guide 264 to eject ink onto a recording sheet 62 for printing. At both sides of the printing region by ink carriage 263 are provided a region called the runway portion provided to bring ink carriage 263 from a stop state to a certain speed and a region called the overrun portion provided to stop ink carriage 263 moving at a constant speed. More specifically, ink carriage 263 runs over the runway portion to prepare for printing from position A to position B in the drawing along scan guide 264. Then, printing is carried out at a constant rate in the printing region. When ink carriage 263 moves passed the printing region to arrive at the overrun portion, ink carriage 263 decelerates and then stops. The change in speed of ink carriage 263 during this travel is as shown in FIG. 1.
Referring to FIG. 2, an ink jet printer 271 disclosed in U.S. Pat. No. 5,831,655 includes a heat roller 274 to transport and apply heat to recording sheet 62 for drying the ink jetted out on recording sheet 62, a recording head 275 located opposite to heat roller 274 to spray out ink on recording sheet 62 for printing, and an exhaust fan 276 for discharging the heat accumulated in ink jet printer 271 outside. Recording sheet 62 is heated by heat roller 274 while ink is sprayed on recording sheet 62 by recording head 275 for printing. Recording sheet 62 continues to be heated by a similar method even after printing. Accordingly, the ink jetted out on recording sheet 62 is dried.
According to ink jet printer 261, a runway portion and an overrun portion are required in addition to the printing region. A region besides the region required for printing must be provided in ink jet printer 261. This accounts for preventing reduction of the size of ink jet printer 261. Ink jet printer 271 has a similar problem since printing is effected in a similar manner.
In ink jet printer 271, the entire heat roller 274 discharges heat. Heat is provided to elements other than recording sheet 62. Heat roller 274 dries one horizontal line at a time on recording sheet 62. Therefore, the size of heat roller 274 per se is great and the heat generated from heat roller 274 is increased. Thus, ink jet printer 271 is increased in size and power consumption. There is also the problem of modification in the quality of the ink caused by recording head 275 being heated since the distance between heat roller 274 and recording head 275 is small. Although cooling is effected by exhaust fan 276 to reduce the heat effect, space and power are required to install and drive, respectively, exhaust fan 276. This also leads to increase in the size and power consumption of ink jet printer 271.
In view of the foregoing, an object of the present invention is to provide a small-size ink jet printer.
Another object of the present invention is to provide a compact ink jet printer that has many and high density of ink heads arranged in the ink carriage.
A further object of the present invention is to provide a compact ink jet printer without deviation between dots in printing.
Still another object of the present invention is to provide a compact ink jet printer without deviation between dots in printing and capable of printing without arc-like distortion.
A still further object of the present invention is to provide a compact ink jet printer without deviation between dots in printing and capable of printing without arc-like distortion, and that can dry printed out ink with lower power.
Yet a further object of the present invention is to provide an ink jet printer that can dry printed out ink without quality modification or coagulation of ink in the ink carriage.
Yet another object of the present invention is to provide an ink jet printer that can dry printed out ink without quality modification of ink sprayed out onto a recording sheet and without deformation of the recording sheet.
Yet a still further object of the present invention is to provide an ink jet printer that can dry printed out ink without quality modification or coagulation of ink in the ink carriage caused by heated air flow generated from a heat generator and that does not deform the spray out of ink droplets jetted out from the ink carriage caused by air blow.
An additional object of the present invention is to provide an ink jet printer that can dry printed out ink without erroneous spray out of ink from the ink carriage and without disturbance in the printed out image or text due to vibration of a heat generator.
Yet an additional object of the present invention is to provide a compact ink jet printer that can carry out printing at high speed.
According to an aspect of the present invention, an ink jet printer includes a shaft provided rotatably about a predetermined axis, a strut fixed to the shaft so as to move along an arc about the axis with rotation of the shaft, an ink carriage having a plurality of ink heads provided at a predetermined position from the shaft of the strut, and a control device controlling forwarding of a recording sheet, rotational motion of the shaft, and ink jetting from the plurality of ink heads.
The scanning operation of the ink carriage is effected by a reciprocating arc motion about the shaft. Therefore, even if the runway portion and the overrun portion of the same running distance as the conventional case are provided along the circular segment, the lateral widths of the runway portion and the overrun portion can be made smaller than those of the conventional ink jet printer. Thus, the travel width in the lateral direction of the ink carriage can be reduced to allow a smaller ink jet printer.
Preferably, the control device controls forwarding of a recording sheet, the rotational motion of the shaft, and ink jetting from a plurality of ink heads by defining the reciprocating motion width of printing for the ink carriage on the basis of the relationship between the width of the reciprocating motion of the ink head out of the plurality of ink heads located farthest away from the shaft and the width of the recording sheet.
The width of the reciprocating motion of printing for the ink carriage is defined on the basis of the relationship between the width of the reciprocating motion of the ink head located farthest away from the shaft and the width of the recording sheet. Therefore, by setting the width of the reciprocating motion of printing for the ink head located farthest from the shaft equal to the width of the recording sheet, printing can be carried out by the ink carriage at the minimum width of the reciprocating motion. Accordingly, the travel width of the ink carriage in the lateral direction can be reduced to allow a more compact ink jet printer.
Further preferably, a maintenance mechanism of the ink carriage is provided outside the printing motion range of the ink carriage, located opposite to the ink carriage.
The maintenance mechanism is provided on the extension of the reciprocating arc motion of the ink carriage. Therefore, the travel width of the ink carriage in the lateral direction can be suppressed to approximately the diameter of the circle at most, i.e., two times the length from the shaft to the leading edge of the ink carriage. Therefore, the ink jet printer can be reduced in size.
Further preferably, the ink carriage includes a plurality of ink heads fixed at the other end of the strut in a radial arrangement.
Since the ink heads are arranged radially, the ink heads can be arranged in an honeycomb manner. The number and density of the ink heads arranged at the ink carriage can be increased.
Further preferably, the control device defines the ink spray out timing from the plurality of ink heads corresponding to the distance between the shaft and each of the plurality of ink heads to control forwarding of a recording sheet, rotational motion of the shaft, and ink jetting from the plurality of ink heads.
Since the ink head moves along an arc, the scanning speed differs depending upon the distance from the strut. The ink spray out timing from the ink head is defined according to the distance from the strut. Therefore, the problem of deviation between dots during printing caused by difference in the scanning speed between ink heads can be eliminated.
According to another aspect of the present invention, an ink jet printer includes two shafts provided rotatably about two predetermined axes arranged at a predetermined distance, two struts fixed to the two shafts, respectively, to move along an arc about two axes with the rotation of the two shafts, an ink carriage having a plurality of ink heads provided at a predetermined position from the shaft of the two struts, and a control device controlling forwarding of a recording sheet, rotational motion of the two shafts, and ink jetting from the plurality of ink heads.
The two shafts, the ink carriage, and the two struts form a link mechanism. Accordingly, the ink carriage can move back and forth along arc. Therefore, even if the runway portion and the overrun portion of the same running distance as the conventional case are provided along the circular segment, the lateral widths of the runway portion and the overrun portion can be made smaller than those of the conventional ink jet printer. Thus, the ink jet printer can be reduced in size. Furthermore, the scanning speed of all the ink heads is identical since the ink carriage moves while maintaining the same posture. Therefore, the problem of deviation between dots during printing caused by difference in the scanning speed between ink heads is eliminated.
Preferably, the control device converts image data according to the curvature of the trajectory of the ink carriage moving back and forth along an arc to control forwarding of a recording sheet, rotational motion of the two shafts, and ink jetting from the plurality of ink heads according to the converted image data.
Therefore, there is the advantage that printing without arc-like distortion is allowed even if the ink carriage moves along an arc.
Further preferably, the control device sequentially prepares data of a predetermined number of lines corresponding to division of image data of one page. The control device converts the prepared data of a predetermined number of the lines according to the curvature of the trajectory of the ink carriage moving back and forth along an arc to control forwarding of a recording sheet, rotational motion of the two shafts and ink jetting from the plurality of ink heads according to the converted data.
Therefore, printing without arc-like distortion is allowed even in the case where image data can be obtained only for every one or plurality of lines such as image data obtained by facsimile and the like.
Further preferably, the ink jet printer includes a heat generator provided at the two struts.
The heat generator carries out a reciprocating arc motion in synchronization with the reciprocating arc motion of the ink carriage. By the heat output from the heat generator, the ink sprayed out on a recording sheet conveyed from the direction of the ink carriage towards the shaft can be dried in parallel to the printing operation. Since the heat generator per se carries out the motion, the entire recording sheet can be dried even if the heat generator is reduced in size. Therefore, power consumption and the amount of heat induced by the heat generator are reduced. An exhaust fan to discharge the heat outside is no longer required. Thus, a smaller ink jet printer can be provided.
Further preferably, the ink jet printer includes a heat generator provided at the leading end of the ink carriage.
The heat generator carries out a reciprocating arc motion in synchronization with the reciprocating arc motion of the ink carriage. Therefore, by the heat discharged from the heat generator, the ink sprayed out on a recording sheet conveyed from the direction of the shaft towards the ink carriage can be dried in parallel to the printing operation. Therefore, the heat generator can be reduced in size, which in turn allows the ink jet printer to be reduced in size. Since the heat generator per se carries out the motion, the entire recording sheet can be dried even if the heat generator is smaller in size. Thus, the power consumed by the heat generator and the amount of heat output from the heat generator can be reduced.
According to another aspect of the present invention, an ink jet printer includes a shaft provided rotatably about a predetermined axis, a strut fixed to the shaft to move along an arc about the axis with the rotation of the shaft, two parallel guide rails, an ink carriage including a plurality of ink heads and that can run along the two guide rails, and that has an opening with the longitudinal direction corresponding to the direction orthogonal to the running direction, and having the end of the strut fitted to allow movement in the opening, and a control device controlling forwarding of a recording sheet, arc motion of the strut, and ink jetting from the plurality of ink heads.
The ink carriage moves along the two guide rails to carry out printing while moving linearly. The scanning operation of the ink carriage is carried out by the strut moving back and forth along an arc. The reciprocating arc motion of the strut is divided into a vertical linear motion in which the strut moves along the opening of the ink carriage and a horizontal linear motion in which the ink carriage runs along the guide rail. Therefore, even if the runway portion and the overrun portion of the same running distance as the conventional case are provided along the circular segment, the lateral widths of the runway portion and the overrun portion can be made smaller than those of the conventional ink jet printer. Thus, the travel width of the ink carriage in the horizontal direction can be set smaller to allow reduction in the size of the ink jet printer.
Preferably, the control device controls forwarding of a recording sheet, arc motion of the strut, and ink jetting from the plurality of ink heads according to image data.
The ink carriage is controlled according to the image data. Therefore, by providing control so that the ink carriage is moved only along the region where printing is carried out and suppressing travel of the ink carriage where printing is not carried out, extra motion of the ink carriage is eliminated to allow high speed printing.
Further preferably, the control device controls forwarding of a recording sheet, the arc motion of the strut, and ink jetting from the plurality of ink heads according to the size of the recording sheet.
Therefore, the operation range of the ink carriage for printing can be limited to that within the recording sheet to eliminate extra motion of the ink carriage. Therefore, printing can be carried out at a high speed.
Further preferably, the portion of the two guide rails coupled with the ink carriage is formed of a ball bearing. The portion of the strut coupled with the ink carriage is formed of a ball bearing.
The junction of the two guide rails and the ink carriage and also the junction of the strut and the ink carriage are respectively formed of ball bearings. Accordingly, abrasion of these junctions is prevented to allow smooth travel of the ink carriage.
According to still another aspect of the present invention, an ink jet printer includes a shaft provided rotatably about a predetermined axis, a strut fixed to the shaft so as to move along an arc about the axis with the rotation of the shaft, an ink carriage having a plurality of ink nozzles spaying out ink in a direction parallel to the plane including the strut, and provided at a predetermined position from the shaft of the strut, and a sheet holding unit holding a sheet at the curvature defined by the relationship with the motion curvature of the ink carriage at a position opposite to the ink carriage.
Printing is carried out by the ink carriage moving along an arc. Therefore, the length of printing required in the horizontal direction can be reduced to allow reduction in the size of the ink jet printer. Also, complicated readout of image data is not required. Therefore, high-speed printout is allowed.
Preferably, the axial direction of the axis is in parallel with the direction of transportation of a sheet.
By this parallel arrangement, the direction of the motion of the ink carriage can be made orthogonal to the direction of transportation of a sheet. It is therefore not necessary to read out image data according to a complicated procedure to generate print data. Therefore, the printout speed can be improved.
Further preferably, the ink carriage has an ink eject plane where a plurality of ink nozzles are formed. The curvature of the ink eject plane is not more than the curvature of the sheet held by the sheet holding unit.
By such a curvature, the contact between the ink carriage and the sheet can be reduced. This provides the advantage that sheet jamming is relatively suppressed.
Further preferably, each of the plurality of ink nozzles ejects ink in the direction of the line connecting the center of the shaft and each ink nozzle.
This provides the advantage that the output direction of ink ejection and the direction of the centrifugal force is in coincidence. Therefore, control of the direction of ink ejection becomes easier. Additionally, the centrifugal force can be utilized in ink ejection to improve the ink ejection speed.
Further preferably, the ink carriage ejects ink by moving back and forth on the same line of a sheet.
By spraying out ink according to a reciprocation motion on the same line, a resolution two times that of ejecting ink at either the forward drive or the backward drive can be obtained.
The ink ejection timing of each of the plurality of ink nozzles is defined according to the distance from the center of the shaft to the ink nozzle, the distance between the ink carriage and the sheet, the position of the ink nozzle, and the speed of ink.
The ink hit position can be calculated according to various parameters. Accordingly, the ink ejection timing can be defined correctly.
Further preferably, the plurality of ink nozzles are arranged on a crossing line between the plane orthogonal to the direction of motion of the ink carriage and the ink eject plane.
By providing the ink nozzles in one row in a direction perpendicular to the direction of motion of the ink carriage, the printing resolution is defined depending on only the travel angle of the ink head.
Further preferably, a sheet size sensor that senses the size of a sheet is further provided. The swing angle of the strut is defined according to the output of the sheet size sensor. Therefore, unnecessary overrunning of the ink carriage can be prevented to allow efficient printout.
Further preferably, the sheet holding unit includes a transportation guide having a cross section of an arc with a concave plane opposite to the ink carriage, and a plurality of transportation rollers arranged to sandwich a sheet with a plane of the transportation guide opposite to the ink carriage.
The sheet is transported by a plurality of transportation rollers arranged circularly along the inner side of the transportation guide. Therefore, the sheet can be transported properly without meander.
Further preferably, the plurality of transportation rollers are jointly driven in the direction of motion of the ink carriage. This provides the advantage that the sheet can be transported uniformly. Therefore, sheet meander and delay in transportation to a certain position can be prevented.
Further preferably, each of the plurality of transportation rollers has a fusiform shape with a curvature smaller than the curvature of the sheet.
This provides the advantage that buckling of the sheet caused by contact with the end of a transportation roller can be prevented.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.